Segmental grinding wheel



Oct. 30, 1934. T." LARSSON SEGMENTAL GRINDING WHEEL Original Filed Sept.4, 1926 flare [arason 'Wdnesses Patented Oct. 30, 1934 UNITED STATESPATENT OFFICE Thure Larsson, Worcester,

Worcester, Mass., a corpora- Norton Company, tion of MassachusettsContinuation of application Serial Mass., assignor to September 4, 1926.This application October 8, 1927, Serial No. 224,989. In Canada August29, 1 18 Claims.

This invention relates to abrasive wheels and more particularly to awheel composed of abrasive segments united into a unitary rigidstructure, and to a method of making the same.

The modern abrasive wheel is ordinarily made by bonding abrasive grains,such as silicon carbide or crystalline alumina, into a structure ofdesired shape. The bond may be any one of various types, such as rubber,sodium silicate, or resinous materials, but more common are ceramicmaterials vitrified to a glassy or porcelanic condition by a suitablefiring operation. The eillciency of a grinding wheel is materiallyimproved by increasing its surface speed, but

owing to the fragile nature of the available bonds, the size and therate of rotation of the wheel is seriously limited. For many grindingoperations it is desirable to use a wheel of a relatively soft grade,but such a wheel ordinarily has only a small amount of bond to hold thegrains in place, and the wheel has but little cohesive strength, so thatit cannot effectively withstand the disruptive forces set up by grindingat a high rotative speed. Furthermore, in

the manufacture of a large wheel made of ceramic bonded abrasive-grains,there is dangen of the wheel being broken during the moulding I andfiring operations, owing to the friable and fragile nature of themoulded article and to the dimculties of firing the body uniformly andpreventing the development of a strained condition in the bond.

In accordance with my invention, a wheel that may be rotated rapidly andyet safely may be made of small segments manufactured separately andthen assembled and united into a unitary wheel structure, and such awheel may be so supported on a rapidly rotated mount that the tendencyfor the wheel to be disrupted by centrifugal force is effectivelyresisted.

It is accordingly one object of my invention to provide a grinding wheelmade of separately fashioned abrasive segments which are fastenedtogether and may be. mounted as a unit on a grinding wheel spindle, andparticularly to provide such a wheel which may be made in diversegrades, shapes and sizes and is capable of givin; a long life ofefficient service when rotated at a high speed.

Further objects are to provide a rotative mount for an abrasive wheelwhich aids materially in strengthening the wheel against disruption bycentrifugal force, and in particular to provide a segmental abrasivebody having 5 suflicient strength for handling and shipment and asupporting structure therefor which supplements the bond strength of thesegments and holds them effectively in place during the grindingoperation.

A further object is to provide an efficient method of making a unitaryabrasive wheel from a number of separately fashioned segments.

With these and other objects in view, as will be apparent to one skilledin the art, my invention resides in the combination of parts set forthin the specification and covered by the claims appended hereto.

One embodiment of my invention is a grinding wheel of a desired sizemade of separately fashioned abrasive segments which may be assembled toform a grinding surface. These are united into an integral wheelstructure by a cementitious bonding material, such as a low meltingmetal, which is capable of holding the segments in position, either forshipment or for grinding usage, thereby forming an abrasive body whichmay be transported independently as a unit and removably mounted as suchon a suitable support. The adhesive strength of the cementitious medium,as well as the coherence of the bond which unites the abrasive grains,may be supplemented by a reenforcing structure which engages aperipheral surface of the wheel and serves to resist any centrifugalforce set up in the inner portion of the wheel.

It is desirable that the filler or cementitious material between thegrinding portions of the segments wear away as fast as and preferably atthe same rate as the abrasive segments wear, and this material may bevaried depending on the type of grinding operation for which the wheelis intended. As an example of a filler which will wear away atsubstantially the same rate as the abrasive wears away for the averagemetal grinding operation, a mixture of sulfur and carbonaceous material,known as lavasul, may be employed. I may use a strong bonding medium,such as Babbitt metal, in the inner spaces of the wheel to hold thesegments securely in place, and a softer, more wearable filler in thecrevices between the segments adiacent to the grinding surface.

The wheel strength may be materially increased by so constructing therotatable wheel mount that it clamps against a peripheral surface on thewheel and preferably against a shoe of suitable material, such as metal,which will make firm contact throughout an extensive area with theclamping support as well as the abrasive body. If the wheel is intendedto grind ing support is substantially equal to the transverse thicknessso that resistance to shearing or cracking is substantially the same inevery direction.

Referring more particularly to the drawing which illustrates a grindingwheel adapted to grind on its peripheral face and in which likereference numerals indicate like parts;

Figure 1 is a perspective view of an abrasive wheel, partly broken awayto show the bonding structure which holds the segments in place;

Fig. 2 is an enlarged sectional view on the line 2-2 of Fig. 1;

Fig. 3 is a perspective view of one of the segments; and

Fig. 4 is a sectional view of a modified form of segment which hasreinforcing members embedded in the shoes.

As illustrated in the drawing, a unitary segmental wheel may comprise anumber of abrasive segments 10 made up of abrasive grains, such ascrystalline alumina or silicon carbide, united in accordance withstandard methods by a suitable bonding material, such as a vitrifiedceramic bond, the structure, porosity and grade of hardness of thebonded mass varying in accordance with the grinding characteristicsrequired. These .segments are made of such sizes and shapes as to becapable of assembly in the required form of grinding wheel and toprovide a suitable grinding surface. If the wheel is to grind on itsperiphery, the assembled segments are shaped as illustrated to form anannulus which has a cylindrical grinding surface 11 and an internalperipheral surface 12. In order to hold the segments rigidly in place, Iprovide a cementitious material which is capable of adhering to thespaced, radial, side faces 13 of the segments and entering their surfacepores, and thereby uniting the segment into a unitary structure. Of thevarious cementitious materials which may be employed for this purpose, Ipreferably utilize a low melting metal, such as a Babbitt alloy of lead,tin and antimony, which may be melted and flowed while hot into theinterstices between the assembled segments. This cementing filler mayserve as the sole medium which units the segments into a rigid integralbody; and it may be supplemented by a reinforcing structure, such as abond, which surrounds a peripheral surface or engages a shoulder of theassembled segments, and preferably one on each side thereof, and therebyresists breakage by the disruptive forces met in the grinding operation,as well as rough handling incident to manufacture and transportation.

In order to carry on a grinding operation, the unitary body of assembledsegments is mounted on a rotary support, and such a support may comprisemembers shaped and arranged to engage supporting and clamping surfaceson the assembled segments. Proper contact may be had between thesupporting members and the abrasive body throughout an extensive surfaceby introducing shoes between the clamping members and the abrasive.These shoes may be made of suitable material which is capable ofabsorbing or distributing the strains set up in mounting and rotatingthe wheel; and they may be inserted as desired between the abrasive bodyand its support, but I prefer to form them on the clamping andsupporting surfaces of the abrasive body so that they are tegraltherewith. This is easily accomplished by casting or otherwise forming asuitable material, such as a low melting metal, in place on the properportions of thesegments. In the form illustrated, the shoes and thecementitious material between the segments are made of the samesubstance and may be formed by a single casting operation.

The abrasive annulus formed of the assembled segments is provided with asuitably arranged clamping shoulder adapted to be engaged by theclamping members of the support, and for this purpose I prefer to form ashoulder on the side of the wheel, and preferably both sides, which islocated at a distance from the grinding surface of the wheel and istherefore out of the way of the grinding operation. The abrasivesegments should fit securely and properly against the supporting surfaceof the rotatable mount, and it is therefore desirable that a shoe orother suitable mediumbe interposed between the inner peripheral surfaceof the abrasive body and its support to absorb and distribute theclamping and rotational strains.

In the form illustrated, the shoulders are on a raised projection 15 oneach side of the abrasive segment, these projections providing an outerperipheral shoulder 16 and an inner peripheral shoulder 1'1 on each sidethereof. The shoulder 16 is preferably located at some distance from theinner shoulder 17 so as to leave a large amount of abrasive materialbetween the clamping shoulders 16 and 1'1; and the distance betweenthese shoulders is preferably so proportioned relative to the thicknessof the segment that the segment is as likely to break transverselybetween the two opposite shoulders 16 and 17, thereby insuring themaximum strength beneath the clamping shoulders to support the abrasivesegment in place under a high rate of rotation and the strains ofgrinding.

The segments of the shape shown in Fig. 3 are assembled as an annuluswith their faces 13 slightly spaced apart, and Babbitt metal is flowedor otherwise placed in the interstices therebetween, forming webs 18 ofmetal which make intimate contact with the segments and unite them.intoan integral body. The clamping shoes 19 and 20 on the shoulders 16 and17 may be formed at the same time by the provision of suitable castingmolds, or if desired they may be separately formed on the individualsegments the webs 18 andbefore assembly. the shoes 19 and 20 areintegral parts of a skeleton frame work, so arranged that the shoessurround the peripheral shoulders 16 and 1'1. The shoe 20 formed on thesurface 17 has a substantially cylindrical inner surface 25 which isadapted to engage a corresponding surface on a support, while the shoe19 preferably has a beveled face 26 which is shaped as the frustum of acone so that a complementally shaped clamping member may have awedge-like action on this surface when drawnv into place, and therebycompressively hold the segment between the two clamping shoes. If it isdesired to utilize a reinforcing member, strengthening wires 27 and 28,as shown in Fig. 4, may be properly positioned in the mold so that theyAs shown,

will lie embedded in the shoes and form strong bands capable of holdingthe segments securely in place as well as strengthen the wheel.

As shown, the metal frame work does not extend outwardly beyond the shoe19, thereby leaving open'fcrevices between the grinding portions of thesegments. These crevices are preferably. filled with a substance 29capable of wearing away as the abrasive body is ground away and ofkeeping the crevices filled substantially to the grinding surface. Asuitable filler for this purpose is a mixture of about of sulfur with40% of pulverized coke, known as lavasul, but it will be understood thatother materials, such as those commonly employed as bonds and cements inthis art, may be used. This filler unites intimately with the abrasivesegments and aids as a bond in strengthening the wheel and particularlyin preventing iniury to the outer corners and edges of the segments.

In the manufacture of such a wheel, the segments of bonded abrasivegrains. previously shaped to form an annulus pf the desired dimensions,may be suitably mbled in their final arrangement, independent of thegrinding wheel support, around a central, upwardly extending,cylindrical portion of structed plate or table. slightly spaced toprovide the crevices within which the cementitious medium may be poured.Suitably shaped forms are placed around and between the segments to formthe shoes and to limit the flow of metal in the radial spaces, so as toleave the outer portions of the crevices for the softer filler. Thesegments may be held in proper place by a band of metal placed aroundthem, and covered by a plate provided with pouring holes arranged tocome directly over the crevices between the segments. Thereafter, moltenBabbitt metal is poured through the holes in thecover plate to fill theunobstructed portions of the crevices between the segments as well asthe annular spaces left for the shoes. This material flows into thesurface pores of the segments and hardens, and thereby bonds thesegments integrally in a rigid and secure man- When the molten metal hascooled and set, the outer unfilled spaces between the segments may befilled with a composition capable of hardening in place, such as amixture of sulfur and carbonaceous material known as lavasul, afterwhich the wheel is ready for use. It will be understood that a singlecementitious medium may. be used alone to fill the crevices and form thewebs 18. Also, they may be formed separately on the individual segments,thereby permitting the segments to be shipped as desired and easilyassembled at the place of use, in which case suitable bonding cement tointegral wheel structure.

A grinding wheel of the type described may not be suiilciently strong tostand the high rate of speed desired for its use, although it is strongenough for transportation and storage and the ordinary handlingoperations incident to manufacture. A further feature of my inventionaccordingly comprises a grinding wheel support which is so constructedandarranged that it will carry an abrasive wheel and add materiallyannulus, so that upon drawing the two clamping and supporting memberstogether, the abrasive body will be securely held in position forgrinding.

A simplified form of clamping and supporting member, as illustrated,comprises two clamping plates 30 and 32 adapted to be suitably mountedon a grinding wheel spindle 33. The plate 32 may be keyed to the spindleand the plate 30 slidably mounted on the reduced end of the shaft andsecured in position by means of a nut 34. The two plates are eachprovided with a shoulder 36 having an external peripheral sur faceadapted to engage and support the inner surfaces 25 of the shoe 20. Eachplate likewise has an inwardly projecting rim 37 near its outer edgewhich has a steeply beveled surface adapted to slidably engage thefrusto-conically shaped surface of the shoe 19. It will therefore beseen slide on the shoes 19 and ccmpressively clamp the segments inposition against the supporting shoulders 36. Whatever the constructionof the abrasive annulus, this form of mount will hold the abrasive bodysecurely in place against the disruptive action of centrifugal force.

Since the clamping plates confine a considerable proportion of the wheelvolume therebetween, it will be seen that the shoes 19 and 20 servelargely as bearings for the clamping surfaces on the plates and that therings 19 and 20 of the frame structure shown inFlg. 1 need have no greatstrength for many types of wheel. In case the bonding webs'l8 may needreinforcement, then it is desirable that the rings 19 and 20 be soconstructed that they will aid in holding the segments together duringthe handling operations incident to manufacture and transportationbefore the wheel is mounted on a grinding machine spindle. These shoesalso locate the wheel correctly on the mount, hence they should beaccurately shaped. Owing to the fact that the clamping rims 37 engagethe wheel close to its grinding portion, a considerable proportion ofthe abrasive body is confined between the plates, and the dangersincident to breakage are minimized.

In accordance with which, for the larger factured inexpensively comparedwith the cost of making the usual form of an integral monolithic wheel.These may be easily assembled and cemented together either before orafter shipment to the point of use. When mounted on the rotatablesupport, the wheel is further reinforced by the strong metal platesemployed for this purpose. Such a wheel may be rotated at an extremelyhigh speed, as is desirable since material removed from the object beingground. by increasing the speed of rotation of the grinding wheel, thecost of grinding. a given article is materially reduced.

This case is a continuation of my application Serial Number 133,531,filed September 4, 1926.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent is:

1. The method of making a grinding wheel lny invention, I have prowhichcomprises assembling a plurality of bonded abrasive segments in spacedrelation in the form of a wheel, and casting a cementitious materialaround a peripheral surface of and between the segments in such a manneras to form a reinforcing structure for supporting and holding thesegments rigidly in position.

2. The method of making a grinding wheel which comprises assembling aplurality of bonded abrasive segments in spaced relation in the form ofa wheel, and forming a cementitious reinforcing structure upon a side ofthe segments having a frusto-conical surface of accurate dimensions toflt a flange for mounting upon a grinding machine.

3. An abrasive wheel comprising a'row of spaced abrasive segmentsarranged independently of any support as an annulus having parallel sidefaces, an inner supporting surface and a peripheral grinding surface, acementitious material between the segments which unites them into anintegral wheel structure, a shoulder on each outer side of the wheellocated at a considerable distance from the inner surface of the annulusand close to that portion of the wheel which is normally intended to beused in the grinding operation, and a shoe integral with each shoulderwhich has a bevelled clamping surface arranged to receive the pressureof a mating clamping member and transmit it to the abrasive body.

4. A grinding wheel comprising a row of ceramic bonded abrasive segmentsarranged as an annulus, a metal cast between the segments and unitingthem ,into an integral body which is independent of the wheel support, ashoe cast on the inner surface of the annulus and forming a seattherefor, and a shoe cast on each outer side of each segment which has abeveled shoulder for engagement with a rotatable clamping member on awheel support.

5. An abrasive segment comprising a body of bonded abrasive grainsshaped to have an outer convex surface, an inner concave surface, tworadially converging faces and two sides, each side having a shoulder, aclamping shoe molded on each shoulder and a seating shoe molded on theinner concave surface.

e. An abrasive wheel comprising a plurality of segments of bondedabrasive grains arranged independently of a support as an abrasiveannulus, and means including a tough cementitious bonding material inthe inner portions of the crevices between the segments and a friablecementitious filler in the outer portions of the crevices capable ofwearing away at approximately the same rate as does the abrasivematerial during the grinding operations which serveindependently of anysupporting member to unite the segments into an integral wheel structurecapable of being transported and mounted as a unit on a rotary support.

7. A grinding wheel comprising bonded abrasive segments arranged as anannulus, a cementitious material in the spaces between the segmentswhich unites them into an integral body independently of the wheelsupport, a shoe integral with the annulus and forming an innerperipheral supporting surface, each segment having clamping shoulders onits opposite outer faces, and a shoe integral with each shoulder andhaving a beveled surface for engagement by a correspondingly shapedmember on a rotatable wheel support.

8. An abrasive wheel comprising a plurality of abrasive segmentsarranged as an annulus which has a peripheral grinding surface, an innersupporting surface and a peripheral shoulder on each of its outer sides,a cementitious filler in the interstices between the segments, andclamping and seating shoes on said inner surface and shoulders which areintegral with said cementitious material, said shoes on the peripheralshoulders forming continuous rings encircling and strengthening thewheel.

9. A grinding wheel comprising a plurality of abrasive segments arrangedas an annulus, each segment having a shoulder on each of its oppositeouter sides, beveled clamping shoes rigidly fixed on the shoulders, ashoe integral with the inner face of the annulus and forming aperipheral seat, a cementitious material in the crevices between thesegments uniting them into an integral body, and removable, reinforcingand supporting members providing a support for said seat and havingclamping members wedgingly and compressively engaging said seat andbeveled shoes and serving to resist the centrifugal force when the wheelis rotated at a high speed.

10. A grinding wheel comprising a plurality of abrasive segments shapedand assembled to form an abrasive annulus having a grinding face and aseating face, each segment having clamping shoulders on opposite sidesthereof, a cementitious filler cast in the interstices between thesegments and rings cast on said clamping shoulders and against saidseating face which are integral with said filler and cooperate to unitethe segments into a rigid wheel structure, said rings serving asclamping and seating shoes for mounting the wheel on a support.

11. An abrasive wheel comprising a plurality of spaced segments ofbonded abrasive grains arranged independently of their rotative-supportas an annulus which has a peripheral grinding surface, parallel sidefaces and an inner seating surface, a cementitious filling material inthe crevices between the segments which supports them laterally and aidsin holding the wheel structure together, shoulders on the outer sides ofeach segment, a shoe integral with each shoulder which has a bevelledclamping surface thereon, removable supporting plates on each side ofthe wheel having supporting surfaces which mate with the seating surfaceand the bevelled shoes on the annulus, and means for clamping the platesagainst the annulus so that they wedgingly engage it and resistdisruption thereof when rotated at high speed.

12. An'abrasive wheel comprising a plurality of spaced abrasive segmentsarranged independently of their rotative support as an annulus having aperipheral grinding face, parallel side faces and an inner seatingsurface, a filler in the crevices between the segments, the annulushaving shoulders on its opposite side faces, means comprising aring-shaped shoe rigidly mounted on each shoulder of the annulus whichreinforces the wheel structure, said shoes having bevelled clampingsurfaces, and clamping plates having mating surfaces wedgingly engagingthe seating and bevelled surfaces of the annulus which support the sameand resist disruption of the wheel when rotated at high speed.

13. An abrasive wheel comprising a plurality of spaced abrasive segmentsarranged independently of their rotative support as .n annulus having aperipheral abrasive face, side faces, an inner seating surface shapedfor engagement which mates with said seating and bevelled surfaces,whereby the wheel may be wedgingly supported when rotated during agrinding operation.

14. An abrasive wheel comprising a plurality of spaced bonded abrasivesegments arranged as an annulus independently of their rotative 15. Anabrasive wheel comprising a plurality of bonded abrasive segmentsarranged independently of their rotative support as an annueach of itsouter sides which is located near but not on the grinding portion of theannulus, a clamping shoe which is fixed rigidly on each shoulder and hasa bevelled clamping surface, and a cementitious filler between thesegments which is capable of keeping the crevices filled and ofprotecting the comers of the segments rotated at high speed.

16. A grinding wheel comprising a row of spaced abrasive segmentsarranged as an annulus independently of their rotative support andshaped to form a peripheral abrasive face.

each side face which are spaced at a considerable distance from the holeface and are shaped to support clamping shoes, a cementitious fillingmaterial between the segments which is capable of wearing away, withinthe grinding portion of the wheel, at substantially the same rate asdoes the abrasive and of keeping the crevices filled and the corners ofthe segments protected during a grinding operation, supporting shoes onthe inner peripheral surfaces of the segments, and bevelled clampingopposed clamping plates arranged to support the wheel.

17. An abrasive wheel comprising a plurality of bonded abrasive segmentsarranged independently of their rotative support as an annulus whichperipheral abrasive face, side faces, an inner shoe retaining surfaceand a peripheral shoulder on each of its sides, a reinforcing ringrigidly secured on each shoulder, a cementitious filler between thesegments which is capable of keeping the crevices filled and ofprotecting the corners of the segments during a grinding operation, saidfiller and rings serving to unite the segments into a rigid wheelstructure which may be transported independently of it's rotativesupsaid inner sursaid wheel having a short bevelled sursaid shoulders.ices between the segments a cementitious filler in the crevwhich aidsthe rings on the exposed sides of the segments, the shoes being soshaped that the wheel may be we ly mounted between two opposed clampingplates and thereby reinforced during use.

THURE LARssoNI

